cmd/ld: host linking support for linux/amd64

Still to do: non-linux and non-amd64.
It may work on other ELF-based amd64 systems too, but untested.

"go test -ldflags -hostobj $GOROOT/misc/cgo/test" passes.

Much may yet change, but this seems a reasonable checkpoint.

R=iant
CC=golang-dev
https://golang.org/cl/7369057

3 files changed, 15 insertions, 11 deletions

diff --git a/src/cmd/8l/asm.c b/src/cmd/8l/asm.c
index a00174c368..3563c0849f 100644
--- a/src/cmd/8l/asm.c
+++ b/src/cmd/8l/asm.c
@@ -128,7 +128,7 @@ adddynrel(Sym *s, Reloc *r)
 
 	// Handle relocations found in ELF object files.
 	case 256 + R_386_PC32:
-		if(targ->dynimpname != nil && !targ->dynexport)
+		if(targ->dynimpname != nil && !(targ->cgoexport & CgoExportDynamic))
 			diag("unexpected R_386_PC32 relocation for dynamic symbol %s", targ->name);
 		if(targ->type == 0 || targ->type == SXREF)
 			diag("unknown symbol %s in pcrel", targ->name);
@@ -139,7 +139,7 @@ adddynrel(Sym *s, Reloc *r)
 	case 256 + R_386_PLT32:
 		r->type = D_PCREL;
 		r->add += 4;
-		if(targ->dynimpname != nil && !targ->dynexport) {
+		if(targ->dynimpname != nil && !(targ->cgoexport & CgoExportDynamic)) {
 			addpltsym(targ);
 			r->sym = lookup(".plt", 0);
 			r->add += targ->plt;
@@ -147,7 +147,7 @@ adddynrel(Sym *s, Reloc *r)
 		return;		
 	
 	case 256 + R_386_GOT32:
-		if(targ->dynimpname == nil || targ->dynexport) {
+		if(targ->dynimpname == nil || (targ->cgoexport & CgoExportDynamic)) {
 			// have symbol
 			// turn MOVL of GOT entry into LEAL of symbol itself
 			if(r->off < 2 || s->p[r->off-2] != 0x8b) {
@@ -175,19 +175,19 @@ adddynrel(Sym *s, Reloc *r)
 		return;
 
 	case 256 + R_386_32:
-		if(targ->dynimpname != nil && !targ->dynexport)
+		if(targ->dynimpname != nil && !(targ->cgoexport & CgoExportDynamic))
 			diag("unexpected R_386_32 relocation for dynamic symbol %s", targ->name);
 		r->type = D_ADDR;
 		return;
 	
 	case 512 + MACHO_GENERIC_RELOC_VANILLA*2 + 0:
 		r->type = D_ADDR;
-		if(targ->dynimpname != nil && !targ->dynexport)
+		if(targ->dynimpname != nil && !(targ->cgoexport & CgoExportDynamic))
 			diag("unexpected reloc for dynamic symbol %s", targ->name);
 		return;
 	
 	case 512 + MACHO_GENERIC_RELOC_VANILLA*2 + 1:
-		if(targ->dynimpname != nil && !targ->dynexport) {
+		if(targ->dynimpname != nil && !(targ->cgoexport & CgoExportDynamic)) {
 			addpltsym(targ);
 			r->sym = lookup(".plt", 0);
 			r->add = targ->plt;
@@ -198,7 +198,7 @@ adddynrel(Sym *s, Reloc *r)
 		return;
 	
 	case 512 + MACHO_FAKE_GOTPCREL:
-		if(targ->dynimpname == nil || targ->dynexport) {
+		if(targ->dynimpname == nil || (targ->cgoexport & CgoExportDynamic)) {
 			// have symbol
 			// turn MOVL of GOT entry into LEAL of symbol itself
 			if(r->off < 2 || s->p[r->off-2] != 0x8b) {
@@ -217,7 +217,7 @@ adddynrel(Sym *s, Reloc *r)
 	}
 	
 	// Handle references to ELF symbols from our own object files.
-	if(targ->dynimpname == nil || targ->dynexport)
+	if(targ->dynimpname == nil || (targ->cgoexport & CgoExportDynamic))
 		return;
 
 	switch(r->type) {
@@ -461,7 +461,7 @@ adddynsym(Sym *s)
 	
 		/* type */
 		t = STB_GLOBAL << 4;
-		if(s->dynexport && (s->type&SMASK) == STEXT)
+		if((s->cgoexport & CgoExportDynamic) && (s->type&SMASK) == STEXT)
 			t |= STT_FUNC;
 		else
 			t |= STT_OBJECT;
@@ -469,7 +469,7 @@ adddynsym(Sym *s)
 		adduint8(d, 0);
 	
 		/* shndx */
-		if(!s->dynexport && s->dynimpname != nil)
+		if(!(s->cgoexport & CgoExportDynamic) && s->dynimpname != nil)
 			adduint16(d, SHN_UNDEF);
 		else {
 			switch(s->type) {
diff --git a/src/cmd/8l/l.h b/src/cmd/8l/l.h
index f88f058e35..f6b164d9e4 100644
--- a/src/cmd/8l/l.h
+++ b/src/cmd/8l/l.h
@@ -126,7 +126,7 @@ struct	Sym
 	short	version;
 	uchar	dupok;
 	uchar	reachable;
-	uchar	dynexport;
+	uchar	cgoexport;
 	uchar	special;
 	uchar	stkcheck;
 	uchar	hide;
diff --git a/src/cmd/8l/obj.c b/src/cmd/8l/obj.c
index dcb8390b97..f06bc5d9dc 100644
--- a/src/cmd/8l/obj.c
+++ b/src/cmd/8l/obj.c
@@ -90,6 +90,7 @@ main(int argc, char *argv[])
 	INITRND = -1;
 	INITENTRY = 0;
 	LIBINITENTRY = 0;
+	linkmode = LinkInternal; // TODO: LinkAuto once everything works.
 	nuxiinit();
 
 	flagcount("1", "use alternate profiling code", &debug['1']);
@@ -125,6 +126,7 @@ main(int argc, char *argv[])
 	flagcount("u", "reject unsafe packages", &debug['u']);
 	flagcount("v", "print link trace", &debug['v']);
 	flagcount("w", "disable DWARF generation", &debug['w']);
+	// TODO: link mode flag
 	
 	flagparse(&argc, &argv, usage);
 
@@ -308,6 +310,8 @@ main(int argc, char *argv[])
 	reloc();
 	asmb();
 	undef();
+	hostlink();
+
 	if(debug['v']) {
 		Bprint(&bso, "%5.2f cpu time\n", cputime());
 		Bprint(&bso, "%d symbols\n", nsymbol);